Race, Ethnicity, Socioeconomic Status, and Chronic Lung Disease in the U.S

Background: Higher socioeconomic status (SES) indicators such as educational attainment and income reduce the risk of chronic lung diseases (CLDs) such as Chronic Obstructive Pulmonary Disease (COPD), emphysema, chronic bronchitis, and asthma. Marginalization-related Diminished Returns (MDRs) refer to smaller health benefits of high SES for marginalized populations such as racial and ethnic minorities compared to the socially privileged groups such as non-Hispanic Whites. It is still unknown, however, if MDRs also apply to the effects of education and income on CLDs. Purpose: Using a nationally representative sample, the current study explored racial and ethnic variation in the associations between educational attainment and income and CLDs among American adults. Methods: In this study, we analyzed data (n = 25,659) from a nationally representative survey of American adults in 2013 and 2014. Wave one of the Population Assessment of Tobacco and Health (PATH)-Adult study was used. The independent variables were educational attainment (less than high school = 1, high school graduate = 2, and college graduate = 3) and income (living out of poverty = 1, living in poverty = 0). The dependent variable was any CLDs (i.e., COPD, emphysema, chronic bronchitis, and asthma). Age, gender, employment, and region were the covariates. Race and ethnicity were the moderators. Logistic regressions were fitted to analyze the data. Results: Individuals with higher educational attainment and those with higher income (who lived out of poverty) had lower odds of CLDs. Race and ethnicity showed statistically significant interactions with www.scholink.org/ojs/index.php/rhs Research in Health Science Vol. 5, No. 1, 2020 49 Published by SCHOLINK INC. educational attainment and income, suggesting that the protective effects of high education and income on reducing odds of CLDs were smaller for Blacks and Hispanics than for non-Hispanic Whites. Conclusions: Education and income better reduce the risk of CLDs among Whites than Hispanics and Blacks. That means we should expect disproportionately higher than expected risk of CLDs in Hispanics and Blacks with high SES. Future research should test if high levels of environmental risk factors contribute to the high risk of CLDs in high income and highly educated Black and Hispanic Americans. Policy makers should not reduce health inequalities to SES gaps because disparities sustain across SES levels, with high SES Blacks and Hispanics remaining at risk of health problems.


Introduction
Although the health effects of socioeconomic status (SES) is well established (Mirowsky & Ross, 2015;Ross & Mirowsky, 1999;Marmot & Bell, 2009;Marmot, 2001Marmot, , 2005, such effects are unequal across racial and ethnic groups Hudson, Bullard, Neighbors, Geronimus, Yang, & Jackson, 2012;Farmer & Ferraro, 2005). While high educational attainment and high income predict better health (Marmot & Bell, 2009;Marmot, 2001), recent research has documented weaker protective effects of SES indicators for racial and ethnic minority groups (Montez, Hummer, & Hayward, 2012;Montez, Hummer, Hayward, Woo, & Rogers, 2011;Zajacova & Johnson-Lawrence, 2016;Zajacova & Lawrence, 2018). Marginalization-related Diminished Returns (MDRs) refer to significantly weaker health effects of SES indicators, particularly educational attainment and income, for the socially marginalized people (e.g., racial and ethnic minorities particularly Blacks and Hispanics), relative to the socially privileged individuals (e.g., non-Hispanic Whites) . The MDRs framework can be viewed as a paradigm shift as it investigates the mechanisms behind poor health of racial and ethnic minority people across the full SES spectrum .
Considerable MDRs , are shown in Blacks and Hispanics compared to Whites, documenting weaker effects of SES on health of racial and ethnic groups . Such MDRs are shown for a wide range of SES indicators such as education (Assari, Farokhnia, & Mistry, 2019;Assari & Mistry, 2018) and income  on various health outcomes.
Bazargan, 2019), disability , hospitalization , and mortality  for Black compare to White individuals.
In a study, highly educated Blacks and Hispanics were found to be exposed to high levels of second-hand smoke exposure . In another study, highly educated and high-income Blacks and Hispanics were more likely to drink alcohol (Assari, Farokhnia, & Mistry, 2019;, smoke cigarette (Assari & Mistry, 2018;Shervin & Ritesh, 2019), and vape e-cigarette (Assari, Mistry, & Bazargan, 2020). This is probably why highly educated and high-income Blacks and Hispanics may be at higher risk of chronic obstructive pulmonary disease (COPD) (Assari, Caldwell, & Bazargan, 2019) and asthma (Assari & Moghani Lankarani, 2018), compared to highly educated non-Hispanic Whites. Increased risk of chronic lung diseases (CLDs) may be particularly important and explain high risk of disability , hospitalization , and mortality  in middle-class Black individuals.
Some of the mechanisms behind these MDRs include societal and structural factors such as residential segregation, extra costs of upward social mobility , and higher level of exposure (Hudson, Bullard, Neighbors, Geronimus, Yang, & Jackson, 2012;Hudson, Puterman, Bibbins-Domingo, Matthews, & Adler, 2013;Hudson, Neighbors, Geronimus, & Jackson, 2016) and sensitivity to discrimination (Assari, Preiser, Lankarani, & Caldwell, 2018) in high SES Blacks. Given the social stratification, SES is followed with less tangible health outcomes for Black than White people. However, less is known regarding the relevance of MDRs to the effects of educational attainment on CLDs.
As a result of MDRs , the health effects of SES indicators such as educational attainment and income are diminished for racial and ethnic minority groups. Thus, diverse race/ethnic groups not only vary in their SES (Navarro, 1991(Navarro, , 1990(Navarro, , 1989) but also how their SES turns to health outcomes Assari, Preiser, & Kelly, 2018). As a result, it is "race/ethnicity and SES" not "race/ethnicity or SES" that generates racial and ethnic health disparities (Navarro, 1991(Navarro, , 1990(Navarro, , 1989 Although high education and income reduces exposure to risk factors overall (Lunau, Siegrist, Dragano, & Wahrendorf, 2015;Hackman, Gallop, Evans, & Farah, 2015), Blacks and Hispanics with high education and income report high level of environmental risk factors such as stress , discrimination , and active and passive exposure to tobacco smoke (Assari & Mistry, 2018;Assari & Bazargan, 2009;Assari, Mistry, & Bazargan, 2020

Design and Setting
This cross-sectional study borrowed data from the PATH-Wave 1 study (Chang et  Institutes of Health (NIH). PATH is a landmark longitudinal study of tobacco use and associated diseases.
The PATH study Wave 1 data collection began on 12 September 2013 and ended on 14 December 2014.
The PATH sample is limited to the civilian non-institutionalized adult residents of the United States. The PATH study original sample design follows a multistage probability sample that recruited a representative sample of households and non-institutional people. The PATH study has used a multi-stage sampling strategy that involves survey weights. The results of the PATH are generalizable to the U.S. population. In this study, 25659 adults were analyzed. The PATH data is a longitudinal collection, however, we only used baseline data (wave 1).

Ethics
The original protocol of the PATH study was approved by the Westat Institutional Review Board (IRB).
All participating individuals signed an informed written consent. All the PATH data were collected, stored, and analyzed anonymously.
Four items were used to measure the lifetime history of COPD, chronic bronchitis, asthma, and emphysema. For example, participants were asked, "Have you ever been told by a doctor or other health professional that you had asthma"? We operationalized CLDs as a dichotomous variable.

Data Analysis
We used survey mode of the SPSS 23.0 (IBM Inc, NY, USA) for data analysis. We re-calculated the standard errors (SEs) thus the statistics addressed the complex design of the PATH sample. Thus, our estimates and inferences are generalizable to the U.S. sample. We ran logistic regression models without and with interaction terms, all in the pooled sample. Model 1 only had the main effects of race, ethnicity, educational attainment, income, and covariates. Model 2 also added the following interaction terms: race × educational attainment, ethnicity × educational attainment, race × income (poverty status), and ethnicity × income (poverty status). In all models, educational attainment and income (poverty level) were the independent variables (IVs), any CLDs was the dependent variable (DV), while age, gender, region, and employment were covariates. Race and ethnicity were the moderators.

Descriptive Statistics
This study included 25,659 American adults who were either White (82.9%) or Black (17.1%). The sample was either Non-Hispanic (83.9%) or Hispanic (16.1%). Table 1 shows descriptive statistics of the overall sample (Table 1). Participants were almost half men and women.  as well as race, ethnicity, and covariates. Based on Model 1, high educational attainment and high income (living out of poverty) were associated with lower odds of CLDs (Table 2).  Model 2 showed significant interactions between race and ethnicity with educational attainment and income (poverty status), suggesting that high educational attainment and high income (living out of poverty) have smaller protective effects against CLDs for Blacks and Hispanics than Whites (Table 3). Outcome: Chronic Lung Diseases (CLDs).

Discussion
Two findings were observed. First, high educational attainment and income (poverty status) were inversely associated with the prevalence of CLDs in the overall sample. Second, Blacks and Hispanics were in a relative disadvantage in comparison to Whites regarding the protective effects of educational attainment and income levels on CLDs. That is, the negative associations between SES indicators (i.e., educational attainment and income level) and CLDs were weaker for Blacks and Hispanics than non-Hispanic Whites. As a result, highly educated and high-income Blacks and Hispanics remain at high risk of CLDs, compared to highly educated and high-income non-Hispanic Whites.
The second observation, that the very same SES indicators (educational attainment and income levels) show considerably weaker effects on CLDs for Blacks and Hispanics than non-Hispanic Whites, is relatively new. Previously, for Blacks, high income and educational attainment were shown to have weaker effects on asthma (Assari & Moghani Lankarani, 2018) and COPD (Assari, Caldwell, & www.scholink.org/ojs/index.php/rhs Research in Health Science Vol. 5, No. 1, 2020 57 Published by SCHOLINK INC. Bazargan, 2019). However, this was never shown for Hispanic people. It was also not shown for CLDs overall.

Limitations
The major limitation of this study is its cross-sectional design. As a result of such design, we do not infer causal effects from our observations. As SES and health have bidirectional associations, reverse causal effect of health on SES cannot be ruled out. Poor health is one of the reasons behind downward social mobility. This study measured CLDs such as COPD and asthma based on self-report rather than physical examination, laboratory testing, or administered data (e.g., insurance claims). Self-reports have been shown to generate valid and reliable measures of chronic diseases (Martin, Leff, Calonge, Garrett, & Nelson, 2000). However, future research may replicate these findings for other ethnic groups, as well as based on immigration status. Future research may also use comprehensive multi-item measures. The study is probably biased by omitted confounders such as wealth and area SES. We did not control for smoking because smoking may be the reason high SES Blacks and Hispanics are at an increased risk of CLDs. Thus, the study did not control for the intermediate / mediator variable. Still, this study had a large sample size and extends what we know regarding the non-linear effects of race, ethnicity, and SES on health outcomes particularly CLDs.

Conclusions
In the United States, the inverse associations between SES indicators (i.e., educational attainment and income) and CLDs are weaker for Blacks and Hispanics than non-Hispanic Whites. As a result, we observe a higher than expected prevalence of CLDs in highly educated and high-income Black and Hispanic people, a rate which is disproportionate to their SES. Researchers should know that health disparities are not merely due to the additive but also multiplicative effects of race, ethnicity and SES.
Real solution to racial and health disparities in CLDs is not only increasing SES of Blacks and Hispanic but also empowering them to translate their available SES resources to health outcomes. Public policies that are needed should go beyond equalizing SES and specifically address societal barriers, environmental risk factors, and structural factors that endanger the health and well-being of Blacks and Hispanics at all SES levels. Economic and public policies are needed to minimize diminished health returns of SES (i.e., MDRs) for racial and ethnic minorities. Unfortunately, contribution of MDRs to racial and ethnic health disparities are historically overlooked in the U.S.